What to Do About High Humidity in Your RV
- Lee Burbank
- Nov 26, 2025
- 6 min read
Updated: Jan 13
Especially this time of year, we see lots of frantic posts on Facebook about people having issues with condensation in their RVs. They see water droplets on their windows, moisture under their mattress, in their closets and in cupboards and dripping from their hatches.
Condensation, a sign of high humidity is a very serious challenge for RVers and one that should not be ignored. The fact is that if you are seeing any of the above signs of high humidity, then chances are very good that there are all sorts of other places you have moisture that you are not seeing.
The Problem
Condensation happens when warm air with a high moisture content meets a cold surface. When warmer, moist air meets a colder surface, the air looses its ability to hold moisture and this causes the water vapor to change from a vapor to liquid water. We could go more into detail but hopefully this answer will suffice for our discussion.
It is really important to remember that condensation is a symptom of high humidity. To rectify it, you must lower the humidity in the air.
Why is an RV more likely to have condensation issues than your house? There are two basic reasons:
1. RVs are not insulated like your “sticks and bricks” house. Insulation prevents walls from being cold and keeps the heat in and the cold out.
2. The area in an RV is much smaller in a home so the moist air produced by cooking, washing dishes, showering and other normal activities of daily living has much less of a chance to be dissipated and is therefore much more concentrated in an RV
High humidity is not just inconvenient. If left unchecked, it can lead to mold and mildew and real costly damage to your home on wheels. High humidity can also damage wood and other materials your RV is constructed with.
Plan Of Attack
After more than 18 years of living full time in RVs in all sorts of climates from South Florida to Arizona and Northern and Southern California, here is a plan of attack.
1. When purchasing a new or used RV, ask:
a. What is the level of insulation in the RV? take a look at this link to learn more about insulation. https://rvshare.com/blog/the-ultimate-guide-to-rv-insulation/ .Especially if you know you will be in high humidity climates like Florida, this should be a major consideration when purchasing.
b. Dual pane windows are a great option. In this type of window, a space of air is place between two panes of glass and will keep the window warmer making the air less likely to condense.
2. Always monitor the humidity level in your RV. You can buy inexpensive humidity monitors like this
Buy a couple and place them in different rooms in you RV. You should always try to keep the humidity level in the low 30s.
3. Air flow is key. Warm air trapped in closed cabinets and closets and meeting a cold outer wall will cause condensation. It will help to always keep closets and cabinets open or partially open to allow for air flow in high moisture situations.
4. Always use your hatches and vent fans. The best procedure is to open a vent and turn on the fan to pull air out. Then open a window near the source of the humidity(cooking, showering, washing dishes etc.). This process will draw air from the outside, mix it with the high moisture air and pull it out of the RV through the vent.
5. You can add extra insulation to cabinets, under the bed etc. It is important to note, however, that this does not fix the problem. It only addresses a symptom. It does not reduce the moisture in the air.
6. Buy a dehumidifier.
A good humidifier that is the compressor type can truly be a game changer. It is incredible the amount of water that it can remove from the air. It does not mean that you do not need to take the preventative measures listed in #2 though #5 above but it can make a huge difference. As full timers, we struggled for years before taking this step.
a. We tried desiccants like “Damp Rid” which are bags that you hang in closets or little tubs that you place around. We found them to be next to useless as they remove only a small amount of water. They also can leak and spread chemical on clothes.
b. We have also tried small “mini dehumidifiers” that use the same principal as the bags above but have a fan and the absorbing material is reusable. We found these to be useless.
c. We also tried a “dryer” which is nothing more than a small heater.
d. In our opinion, the only meaningful dehumidifier solution is one with a heat pump. This solution costs a bit more, is somewhat larger and has a compressor as its main component. It also produces slightly warm air in its discharge of dry air. We found this solution truly amazing in the difference it made. We emptied gallons of water daily until we got the humidity level down. We placed our unit in the bathroom at the rear of our 40 foot motorhome and it reduced the humidity dramatically in the entire coach. We wished we had done this years ago!!! We wish that we could recommend the dehumidifier that we used ,but the company Tosot no longer makes dehumidifiers. Amazon has a huge selection. A couple of tips when buying one.
ignore the square footage recommendations. Get as large a one as you can possibly fit in the space allotted.
get one with as large a water holding tank as possible unless you somehow have a low point where you can drain to a hole in the floor. Some versions have pumps that can pump up to a sink. We have never tried that. We would empty the holding tank in ours about twice day.
Additional Note:
We originally purchased a Levoit Dehumidifier, but this brand stopped making them. It was an excellent product.
Based on research, this brand at the link below, Waykar, is well reviewed and we believe would make a good alternative.
Our experience is that you should purchase one many times the actual square footage of your RV for it to really make a difference.
It removes a lot of moisture daily (up to 80 pints), so it handles dampness well even in larger RV spaces.
It’s Energy Star certified, meaning it uses less power, which is good for saving energy on the road.
The unit is fairly quiet and lightweight with wheels, so it won’t disturb or be hard to move around.
You can empty it manually via a tank or hook up a hose for continuous drainage, which is convenient for RV setups.
The controls are simple and let you set humidity levels and timers easily.
It might sound like "over kill" with the square feet and all, but it is not, believe me. Remember the huge difference in the insulation between a house and your rv.
Overall, it’s a solid, efficient option that’s easy to use and effective at keeping an RV dry
Posted on November 6, 2020 by RV Living Full Time
How to get better air flow from bedroom roof a/c unit or any air flow?
John
RVlivingfulltime.com says:
Morning John,
Great question. We have the same issue in our motorhome and there are two possible solutions and we are using both.
The idea of both of these possible solutions is to cut off the air flow, or reduce it to the areas of your RV that have ample air flow and force that air to the other areas of the RV that need more air flow.
1. You can buy new vents on line on Amazon that have louvers that you can close.They are kinda pricey. This will force more air to other vents in the motorhome. The vents are really easy to replace. Most of ours just pull out and then you can push in the new ones.
2. A less expensive and equally effective solution is to cut circular pieces of cardboard that will just fit the vent. Then you take off the vent, and tape the piece of card board to the back of the vents thereby blocking the air from coming out. We tape them to the vent as we didn’t want to risk that somehow the piece of cardboard could get blown off the vent and go into the duct work.
Let me know how these possible solutions work.
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